This invention relates to a forming method of a magnetic recording medium protective film characterized by forming a monomolecular adsorption film on a substrate of magnetic recording medium by chemical reaction after preliminarily forming a metal oxide film thereon.
Hitherto, for practical use of magnetic disc developed in the field of electronics, enhancement of wear resistance of the magnetic substrate surface has been indispensable in performance.
For example, a magnetic recording substrate composed of chromium (Cr), nickel (Ni) and cobalt (Co) is very soft on the surface in its structure made of these components alone, and the wear resistance of the substrate surface must be improved by coating with a lubricant after evaporating carbon.
Since the conventional protective films of magnetic recording substrate were formed by coating with a lubricant in the manufacturing process, the uniformity of the film thickness on the substrate was poor, the adhesion between the substrate and film was inferior, and the durability was low.
On the other hand, it had been also attempted to use a chemical adsorption film as the protective film of magnetic recording substrate (e.g. U.S. Pat. No. 4,761,316), but since the adsorption film was formed on the substrate without forming an oxide film which is indispensable for adsorption reaction, the molecular density in the adsorption film was very low and, consequently, the wear resistance was poor, and it was not sufficient as a lubricating film.